Electromagnetic forming apparatus



Dec. 1, 1970 R 3,543,550

ELECTROMAGNETIC FORMING APPARATUS Filed July 17, 1968 POWER 1 SUPPLY INVEH TOR A T TORNEY nited States ate 3,543,550 ELECTROMAGNETIC FORMING APPARATUS David J. Rose, Waban, Mass., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 17, 1968, Ser. No. 745,540

Int. Cl. B21d 26/14 US. C]. 72-56 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an apparatus for electromagnetically forming a conductive workpiece, and more particularly to an electromagnetic forming apparatus which is capable of accommodating the installation and removal of an irregularly shaped workpiece into and out of the workspace.

Typically, in the electromagnetic forming process, a conductive workpiece is disposed within a workspace defined by the interior opening of an electromagnetic coil. The electromagnetic coil is energized so as to generate a high intensity time varying magnetic field within the Workspace so that a large current is induced in the workpiece. The induced current in the workpiece interacts with the magnetic field within the workspace so as toproduce a forming force on the workpiece.

In order to obtain optimum coupling of magnetic energy between the electromagnetic coil and the workpiece, the electromagnetic coil is ordinarily shaped so as to fit closely around the section of the workpiece to be formed thereby providing a compact workspace. However, this confined electromagnetic coil arrangement presents a severe disadvantage Where the workpiece is irregularly shaped and includes a section larger than the section to be formed. Due to the constricted shape of the electromagnetic coil, the interior opening is too small to accommodate the insertion and removal of a workpiece having a section larger than the workspace. If the electromagnetic coil is enlarged or distorted so as to provide space for admitting an irregularly shaped workpiece, the distance between the electromagnetic coil and the workpiece is substantially increased thereby seriously reducing the magnetic energy transmitted from the electromagnetic coil to the workpiece so that the workpiece is not properly formed.

Accordingly, it is an object of this invention to provide an electromagnetic forming apparatus having relatively movable electromagnetic coils so as to accommodate the installation and removal of an irregularly shaped workpiece into and out of the workspace without appreciably diminishing the magnetic energy transmitted to the workpiece during the forming operation. In order to accomplish this object, one embodiment of the invention comprises a primary coil and a secondary coil which are relatively movable between a forming position and a transfer position. In the forming position the secondary coil is disposed within the interior opening of the primary coil so as to define a Workspace for the workpiece be tween the primary coil and the secondary coil so that the secondary coil conveys magnetic energy from the primary coil to the workpiece. In the transfer position the secondary coil is disposed without the interior opening of the primary coil sothat an irregularly shaped workpiece may be installed within and removed from the workspace through the interior opening of the primary coil.

It is another object of this invention to provide an electromagnetic forming apparatus having relatively movable electromagnetic coils so as to permit an irregularly shaped workpiece to be laterally installed within and removed from the workspace. In order to accomplish this object, another embodiment of the invention contemplates a primary coil and a secondary coil which are relatively movable as previously described. In addition, both the primary coil and the secondary coil are constructed so as to extend approximately within two substantially perpendicular planes. Thus, in the transfer position the interior opening of the primary coil provides a passage extending laterally into the workspace so that the workpiece may be laterally transferred into and out of the Workspace through the interior opening of the primary coil.

These and other objects will become more apparent by reference to the following detailed description of the preferred embodiments when considered in conjunction with the accompanying drawing, in which:

FIGS. 1 and 2 are perspective views of one embodiment of the electromagnetic forming apparatus of the invention.

FIG. 3 is an enlarged view of one portion of the illustrated embodiment of the inventive electromagnetic forming apparatus.

FIGS. 4 and 5 are perspective views of another embodiment of the electromagnetic forming apparatus of the invention.

FIG. 6 is a schematic diagram of a current source which may be used in cooperation with the illustrated embodiments of the inventive electromagnetic forming apparatus.

Referring generally to FIGS. 1, 2, 4 and 5, the illustrated electromagnetic forming apparatus of the invention comprises a primary coil 10, 10, a secondary coil 12, 12' and a motive device 14, 14' for relatively moving the primary coil 10, 10 and the secondary coil 12, 12. The single turn primary coil 10, 10 is provided by a bar conductor 16, 16 fashioned in the form of an elongated loop so as to define an interior opening 18, 18'. The primary coil 10, 10' includes a pair of input terminals 20, 20" and 22, 22'. The secondary coil 12, 12' is provided by a slab conductor 24, 24' fashioned in the form of an elongated plate. The motive device 14, 14' is provided by a drive motor 26, 26 which is connected to the secondary coil 12, 12 by an arm 28, 28'.

An irregularly shaped conductive workpiece 30, as best viewed in FIGS. 1 and 4, comprises a tubular section 32 and a yoke section 34 having a hub portion 36. The end of the tubular section 32 is to be clamped to the hub portion 36 of the yoke section 34 by the application of an electromagnetic forming force.

Referring particularly to the embodiment of the inventive electromagnetic forming apparatus shown in FIGS. 1 and 2, the bar conductor 16 is fashioned so that the elongated loop forming the single turn primary coil extends approximately within a single plane. Likewise, the slab conductor 24 is fashioned so that the elongated plate forming the secondary coil 12 extends approximately within a single plane. The drive motor 26 maneuvers the secondary coil 12 by rotation as indicated by an arrow 38 between a transfer position as illustrated in FIG. 1 and a forming position as illustrated in FIG. 2.

In the forming position the secondary coil 12 is disposed within the interior opening 18 of the primary coil 10 so as to define a workspace 40 for the workpiece 30 between one end 42 of the primary coil 10 and one end 44 of the secondary coil 12 as shown in FIG. 3. In the transfer position the secondary coil 12 is disposed without the interior opening 18 of the primary coil 10 so that the irregularly shaped workpiece 30 may be installed Within and removed from the interior opening 18 of the primary coil 10 by rotating the workpiece 30 as indicated by an arrow 46. The yoke section 34, which is larger than the workspace 40, is easily accommodated by the interior opening 18 as the workpiece 30 is transferred into and out of the primary coil 10.

Referring particularly to the embodiment of the inventive electromagnetic forming apparatus shown in FIGS. 4 and 5, the bar conductor 16 is fashioned so that the elongated loop forming the single turn primary coil 10' extends approximately within two substantially perpendicular planes. Similarly, the slab conductor 24' is fashioned so that the elongated plate forming the secondary coil 12' extends approximately within two substantially perpendicular planes. The drive motor 26' maneuvers the secondary coil 12' by translation as indicated by an arrow 48 between a transfer position as shown in FIG. 4 and a forming position as shown in FIG. 5.

In the forming position the secondary coil 12' is disposed within the interior opening 18 of the primary coil 10 so as to define a workspace 40 for the workpiece 30 between one end 42 of the primary coil 10' and one end 44 of the secondary coil 12' as again shown in FIG. 3. In the transfer position the secondary coil 12 is disposed without the interior opening 18' of the primary coil 10' so that the irregularly shaped workpiece 30 may be installed within and removed from the interior opening 18 of the primary coil 10' by laterally translating the workpiece 30 as indicated by an arrow 50. The yoke section 34, which is larger than the workspace 40, is again easily accommodated by the interior opening 18 as the workpiece 30 is transferred into and out of the primary coil 10".

Thus, in both of the previously described embodiments of the inventive electromagnetic forming apparatus, the motive device 14, 14' relatively maneuvers the primary coil 10, 10 and the secondary coil 12, 12' between a forming position and a transfer position. In the forming position the secondary coil 12, 12 is disposed within the interior opening 18, 18' of the primary coil 10, 10' so that a workspace 40 for the workpiece 30 is defined between the primary coil 10, 10' and the secondary coil 12, 12'. In the transfer position the secondary coil 12, 12' is disposed without the interior opening 18, 18 of the primary coil 10, 10' so that the workpiece 30 may be transferred into and out of the interior opening 18, 18' of the primary coil 10, 10.

Referring particularly to FIG. 3, with the irregularly shaped workpiece 30 positioned within the workspace 40 between the primary coil 10, 10 and the secondary coil 12, 12, the end of the tubular section 32 may be deformed about the hub portion 36 of the yoke section 34 by the application of an electromagnetic forming force. This may be accomplished by energizing the primary coil 10, 10' thereby energizing the secondary coil 12, 12' so that together the primary coil 10, 10' and the secondary coil 12, 12' generate a high intensity time varying magnetic field within the workspace 40 so as to produce a forming force on the workpiece 30.

FIG. 6 illustrates a typical current source which may be used in cooperation with the previously descr d bodiments of the inventive electromagnetic forming apparatus. The current source includes a high voltage power supply 52, a manually operable power switch 54, a capacitor bank 56, and a spark gap 60. The current source also includes a pair of output terminals 62 and 64 which are adapted to be connected to the input terminals 20*, 20' and 22, 22 of the primary coil 10, 10'.

The electrical operation of the illustrated embodiments of the inventive electromagnetic forming apparatus may be best understood by referring to FIGS. 3 and 6. When the manually operable power switch 54 is closed, current at the voltage of the power supply 52, for example 10 kilovolts is supplied to the capacitor bank 56. The capacitor bank 56 then charges to some predetermined voltage at which the spark gap 60 breaks down and becomes conductive. As the spark gap 60 conducts, a high energy current pulse of short duration, for example 100,000 amperes for 10 microseconds, is supplied to the primary coil 10, 10 and flows through the elongated loop formed by the bar conductor 16, 16' as indicated by the arrows 66.

The primary current in the primary coil 10, 10' induces a large secondary current in the secondary coil 12, 12 which circulates around the outer edge of the elongated plate formed by the slab conductor 24, 24' as indicated by the arrows 68. The primary current 66 and the secondary current 68 combine to yield a resultant current which flows clockwise about the workspace 40 so as to generate a high intensity time varying magnetic field within the workspace 40. The magnetic field within the Workspace 40 induces a large current in the end of the tubular section 32 of the workpiece 30- as indicated by the arrows 70. The induced current 70 in the end of the tubular section 32 interacts with the magnetic field within the Workspace 40 so as to produce a forming force which collapses the end of the tubular section 32 about the hub portion 36 of the yoke section 34 of the workpiece 30.

Thus, magnetic energy is directly transmitted from the primary coil 10, 10' to the workpiece 30 and is indirectly transmitted from the primary coil 10, 10' through the secondary coil 12, 12' to the workpiece 30. In order to achieve optimum direct coupling of magnetic energy to the workpiece 30, the end 42 of the primary coil 10, 10' is shaped so as to substantially conform to the outer periphery of the tubular section 32 of the workpiece 30. In order to achieve optimum indirect coupling of magnetic energy to the workpiece 30, the end 44 of the secondary coil 12, 12' is shaped so as to substantially conform to the inner periphery of the primary coil 10, 10' and to the outer periphery of the tubular section 32 of the workpiece 30. However, the primary coil 10, 10' the secondary coil 12, 12 and the workpiece 30 are electrically isolated from each other so as to avoid a short circuit.

It is to be understood that the primary coil 10, 10' and the secondary coil 12, 12 of the invention are not confined to the single turn coil structures illustrated in the preferred embodiments but may be constructed of any desired number of turns necessary to produce the required magnetic field within the workspace 40. Accordingly, the secondary coil 12, 12' need not be in the form of a plate, but may also take the form of a loop similar to the primary coil 10, 10'. Likewise, within the limits of the general shapes previously described, the primary coil 10, 10 and the secondary coil 12, 12' may assume whatever specific shapes are necessary in order that the shape of the workspace 40 is adequate to properly deform the workpiece 30 and in order that the shape of the interior opening 18, 18 of the primary coil 10, 10' is adequate to accommodate the irregularly shaped workpiece 30 as it is transferred into and out of the primary coil 10, 10. Similarly, the primary coil 10' need not extend approximately within two substantially perpendicular planes, but may extend within two planes arranged at any desired angle. Preferably, the bar conductor 16, 16' of the primary coil 10, 10' and the slab conductor 24, 24"

of the secondary coil 12, 12 are made of a highly conductive material such as copper. In addition, the primary coil 10, and the secondary coil 12, 12 may be reinforced and insulated in an appropriate manner.

As will be readily appreciated, various current sources other than that shown may be employed in conjunction with the illustrated embodiments of the inventive electromagnetic forming apparatus. For example, the capacitor bank 56 may be replaced by a motor-generated set, and the spark gap 60 may be replaced by a thyratron or an ignitron. Similarly, the drive motor 26, 26', which may take the form of any suitable pneumatic, hydraulic or electric motor, may be replaced by any motive device capable of maneuvering the primary coil 10, 10' and the secondary coil 12, 12' in the prescribed manner. For instance, the secondary coil 12, 12' may be mounted on a workpiece support fixture so as to move with the workpiece 30 as the support fixture is maneuvered by a motive deivce. Further, either the primary coil 10, 10' or the secondary coil 12, 12', or both the primary coil 10, 10' and the secondary coil 12, 12' may be moved by the motive device.

It is also to be noted that the electromagnetic forming apparatus of the invention may be employed to form a variety of different workpieces other than the workpiece 30 which is shown for purposes of demonstration only. The workpiece 30 may be supported in any appropriate support fixture and may be installed within and removed from the workspace 40 in any suitable manner.

It will now be appreciated that a principal advantage of the electromagnetic forming apparatus of the invention is that an irregularly shaped workpiece may be transferred into and out of the workspace without adversely effecting the normal electromagnetic forming of the workpiece. In addition, one embodiment of the inventive electromagnetic forming apparatus permits an irregularly shaped workpiece to be laterally inserted within and removed from the workspace so as to make the inventive apparatus particularly adaptable for use with automatic transfer equipment of the type requiring that the workpiece be laterally transferred with respect to the workspace.

The invention is to be limited only by the following claims.

What is claimed is:

1.- An apparatus for electromagnetically forming a conductive workpiece, comprising: a primary bar conductor fashioned in the form of a loop having an inner periphery generally providing an interior opening and including a workspace defining portion; a secondary slab conductor fashioned in the form of a plate having an r outer periphery generally conforming to the inner periphery of the primary conductor except for a workspace defining portion; means for relatively moving the primary conductor and the secondary conductor into a forming position in which the secondary conductor is disposed within the interior opening of the primary conductor so as to define a workspace for the workpiece between the workspace defining portions of the primary conductor and the secondary conductor, and for relatively moving the primary conductor and the secondary conductor into a transfer position in which the secondary conductor is disposed without the interior opening of the primary conductor so that an irregularly shaped workpiece may be inserted within and removed from the workspace by passing it through the interior opening of the primary conductor; and means for energizing the primary conductor thereby energizing the secondary conductor so that together the primary conductor and the secondary conductor generate a high intensity time varying magnetic field within the workspace when in the forming position so as to produce a forming force on the workpiece.

2. An apparatus for electromagnetically forming a conductive workpiece, comprising: a primary bar conductor fashioned in the form of an elongated loop having an inner periphery generally providing an interior opening and including a workspace defining portion at one end of the elongated loop; a secondary slab conductor fashioned in the form of an elongated plate having an outer periphery generally conforming to the inner periphery of the primary conductor except for a recessed Workspace defining portion at one of the elongated plate; means for relatively moving the primary conductor and the sec ondary conductor into a forming position in which the secondary conductor is disposed within the interior opening of the primary conductor so as to define a workspace for the workpiece between the workspace defining portions of the primary conductor and the secondary conductor, and for relatively moving the primary conductor and the secondary conductor into a transfer position in which the secondary conductor is disposed without the interior opening of the primary conductor so that an irregularly shaped workpiece may be inserted within and removed from the workspace by passing it through the interior opening of the primary conductor; and means for energizing the primary conductor thereby energizing the secondary conductor so that together the primary conductor and the secondary conductor generate a high intensity time varying magnetic field within the workspace when in the forming position so as to produce a forming force on the workpiece.

3. An apparatus for electromagnetically forming a conductive workpiece, comprising: a primary bar conductor fashioned in the form of an elongated loop extending approximately within a single plane, the primary conductor having an inner periphery generally providing an interior opening and including a workspace defining portion at one end of the elongated loop; a secondary slab conductor fashioned in the form of an elongated plate extending approximately within a single plane, the secondary conductor having an outer periphery generally conforming to the inner periphery of the primary conductor except for a recessed workspace defining portion at one end of the elongated plate; means for relatively moving the primary conductor and the secondary conductor into a forming position in which the secondary conductor is disposed within the interior opening of the primary conductor so as to define a workspace for the workpiece between the workspace defining portions of the primary conductor and the secondary conductor, and for relatively moving the primary conductor and the secondary conductor into a transfer position in which the secondary conductor is disposed without the interior opening of the primary conductor so that an irregularly shaped workpiece may be inserted within and removed from the workspace by passing it through the interior opening of the primary conductor; and means for energizing the primary conductor thereby energizing the secondary conductor so that together the primary conductor and the secondary conductor generate a high intensity time varying magnetic field within the workspace when in the forming position so as to produce a forming force on the workpiece.

4. An apparatus for electromagnetically forming a conductive workpiece, comprising: a primary bar conductor fashioned in the form of an elongated loop extending approximately within a pair of mutually perpendicular planes, the primary conductor having an inner periphery generally providing an interior opening and including a workspace defining portion at one end of the elongated loop; a secondary slab conductor fashioned in the form of an elongated plate extending approximately within a pair of mutually perpendicular planes, the secondary conductor having an outer periphery generally conforming to the inner periphery of the primary conductor except for a recessed workspace defining portion at one end of the elongated plate; means for relatively moving the primary conductor and the secondary conductor into a forming position in which the secondary conductor is disposed within the interior opening of the primary conductor so as to define a workspace for the workpiece between the workspace defining positions of the primary conductor and the secondary conductor, and for relatively moving the primary conductor and the secondary conductor into a transfer position in which the secondary conductor is disposed without the interior opening of the primary conductor so that an irregularly shaped workpiece may be inserted within and removed from the workspace by passing it through the interior opening of the primary conductor; and means for energizing the primary conductor thereby energizing the secondary conductor so that together the primary conductor and the secondary conductor generate a high intensity time varying magnetic field within the workspace when in the forming position so as to produce a forming force on the workpiece.

References Cited UNITED STATES PATENTS 3,252,313 5/1966 Eilers et a1. 29 421 3,347,074 10/1967 Eilers et a1. 7256 3,365,923 1/1968 Schenk 7255 3,383,890 5/1968 Wildi 72-56 3,423,978 1/1959 Kline 72 55 RICHARD J. HERBST, Primary Examiner 

